In games nowadays, textures are always the easiest to run.(especially on nVidia cards, as nVidia cards have significantly higher texture fill rates compared to AMD cards) I always max these out with no issue. Resolution, AA, and AF are usually have the most immediate impact to frame-rate.(AMD cards do better in this department, as AMD cards have insane pixel fill rates) Shadows as well, depending on the game. View Distance is is a big one as well, but it only really impacts performance in open world games like ARMA or Borderlands or RTS Games.